Binder product and process



United States Patent 3,159,505 BINDER PRQDUCT AND PROQESS Hovey M. Burgess, Battle Creek, Mich, and James H. Johnson, Kankakee, IiL, assignors to General Foods Corporation, White Plains, N.Y., a corporation of Delaware No Drawing. Filed June 28, 1961, Ser. No. 120,204 13 Claims; (Cl. 127-32) This invention relates to the manufacture of binder material and, more particularly, to the manufacture of a high density core binder from corn and like highstarch materials.

Heretofore, cereal binders made from cereals such as corn have been produced by a wet milling or a dry milling process. In the wet milling process, a slurry of starch, usually corn starch, is drum dried to yield a gelatinized or ruptured product. The bulk density of this product can'inadvertently vary over a considerable range and is diflicult to control, since it depends on such factors as the amount of heat applied to the rolls and the thickness of the starch film on the rolls.

In the dry milling process, the starting material conventionally is com grits, a coarse and relatively expensive granulation fraction of degerminated, dehulled corn. The corn grits are moistened and steamed to a predetermined moisture content and temperature and then passed between heated rolls and, if necessary, dried and ground to a desired fineness. Binders and particularly foundry core-binders of varying densities can be manufactured by this procedure. The majority of foundries employ a high density binderand such a procedure as flaking tempered corn grits does allow the manufacture of a high density core binder. nique is quite difficunlt to control in producing high density core binder material having uniform foundry properties and, indeed, it is not unusual to find that a major part of the starch from the dry milling process is ungelatinized. A need exists, therefore, in the foundry art for a high density core binder having consistent and uniform foundry properties. Furthermore, by reason of the prolonged period of time called for in this dry milling technique, e.g., at least about two hours, such production of core binder is cumbersome. Also, this approach utilizes a prime product (i.e., grits) which are readily salable to the brewery and cereal industries at a much greater profit to the manufacturer.

Moreover, in the case of core binder now manufactured.

by both the dry corn and wet corn milling industries, many foundry workers find it necessary to add additional carbohydrates to the binder material in the form of dextrose and dextrins in order to improve the adhesive properties of the binder. This practice is obviously inconvenient and introduces potential error in core binder formulation.

It is an object of the present invention, therefore, to provide a process utilizing relatively inexpensive highstarch material and which is relatively simple, rapid and readily controlled, and will yield a binder composition of consistently high quality and high density.

It is a further object of the invention to provide a binder composition which possesses the requisite amount of carbohydrate material in the form of soluble solids available for binding core sand together faithfully and uniformly without addition of extraneous carbohydrates.

The present invention is, founded on the discoverey that inexpensive sources of high-starch material, for example, the finer granulation fractions of farinaceous materials such as corn endosperm, can be utilized in the manufacture of a high density core binder by: first uni formly prewettingand/or steaming these materials to a level of 20-30%, preferably 23 to 28% moisture, heat- But, this hot rolling techthe confined area of high pressure within the extrusion vessel and then collapses to a volume which is still in excess of the extrusion orifice volume. Throughout this extrusion cooking operation and the kneading incident thereto, gelatinization of the starch material proceeds but only to the extent that a controlled amount of soluble starch degradation products. are produced. The extrudate, upon emergence from the extrusion cooker, initially expands about 200 to 400% in volume from the shape produced by the extrusion die and thereafter collapses in a few seconds to a hot plastic mass of about 1 /2 to 2 times the volume of the die opening of the extrusion cooker. It is a feature, therefore, of the present invention that only a partial evaporation of moisture takes place as the kneaded dough mass issues from the extrusion orifices, the extrudate retaining during such issuance a majority of the weight precent of moisture present in the mass prior to its extrusion; usualy the dough mass will undergo an evaporation of 20 to 30% of its water content depending upon the extrusion cooking conditions observed.

The moist, farinaceous material is worked or kneaded in the extrusion cooker by the movement of such mechanical elements such as the flights of an auger screw rotating within a cylindrical chamber and advancing the kneaded mass thereby produced toward the extrusion orifice, where it works against a high back pressure due to the limited cross-sectional area of the extrusion die openings therein. Such increases in pressure may be produced by a variety of apparatus. The apparatus utilized should operate in such a way that the dough mass does not exceed 400 F., and preferably the extrudate is initialy in the range of 300 to 350 F. The collapsed extrudate, if allowed to cool to ambient temperature, will assume a glassy, horny appearance and have a moisture content generally in the range of 15 to 22%. The heat treatment which the farin-aceous, high starch fractions undergo is not prolonged to the point at which excessive starch degradation to the form of soluble solids is produced. Preferably, the final product recovered after further drying and granulation of the extrudate will have a soluble solids level ranging from 18 to 30%,

preferably 22 to 28%, by weight of the total binder com-' position produced, soluble solids being those which are recovered as filtrate when the binder material is blended with an excess of water at room temperature and filtered.

Treatment of the extrudate will to some extent be influenced by the design of the extrusion cooking apparatus but is more a function of the back pressure created at the die discharge. The die member at the terminal end of the extrusion cooker should have a sufficient plurality of die openings therein so that the back pressure produced by the die plate is uniformly distributed throughout the extrusion cooker so as to produce a substantially uniform product; preferably a plurality of die openings having sizes ranging from A" to /1" in major cross-sectional dimen? sions are uniformly spaced along the face of the die plate. In this way the proper kneading action is produced between the mechanical working elements of the extrusion cooker and the farinaceous material so that substantially all of the starch cells of the material are ruptured and heat treated to a point where they undergo loss of birefringence when viewed under polarized light.

The moisture content of the farinaceous material as it is fed to the extrusion cooker is critical, since it is important that a controlled amount of frictional heat be generated by the working surfaces of the extrusion cooker. At moisture levels below 20% the amount of torque required to move these working surfaces relative to each other to generate this heat is excessive and, furthermore, the amount of heat which is generated is so great that the starch undergoes an inordinate amount of degradation with a consequent level of soluble solids in the extruded binder composition above that which is desired. On the other hand, at moisture levels above 30% the worked farinaceous corn fractions are too plastic or fiuid to generate the requisite degree of frictional heat for starch degradation incident to the extrusion cooking operation. At moisture levels below 20% and above 30% the final product does not possess the consistently and uniformly excellent foundry properties desired.

The heat treatment which the kneaded mass undergoes during extrusion cooking may be a function solely of the frictional heat existing between the kneading mechanical elements of the extrusion cooker or of such heat in combination with the external heat supplied to the kneaded mass as it is treated. Thus, the invention contemplates that hot water or steam may be directly injected into the system or brought into heat exchange relationship with the barrel of the extrusion cooker and/or the rotating or reciprocating kneading elements within this barrel, all of which constructions are well known to those skilled in the art; it has been found, however, to be preferred practice to rely principally upon the heat generated by the mechanical kneading elements themselves.

While this invention should not be understood as restricted to any particular theory, it is believed that the starch particles are ruptured mechanically by reason of the shearing forces between the particles themselves and the particles and the mechanical working surfaces of the extrusion cooker. Also, it is believed that issuance of the kneaded mass of farinaceous material through the die openings induces further starch rupture. In any event, when the starch product of the present invention is viewed microscopically, substantially all of the starch cells, i.e.,

at least 90% by number, appear to have been ruptured.

The extrudate, after it collapses upon emergence from the extrusion cooker, is hot and plastic, and special cutting means must be employed to subdivide the lengths of material produced, which lengths may range anywhere from A" to 1" depending upon the particular apparatus em ployed to subdivide the extrudate. The relatively tough plastic lengths are subdivided by means of a cutting instrument, such as the rapidly rotating knives of a corn chopper. Typically, lengths of are formed and deposited onto a suitable dryer screen where the pieces are carried down to a moisture level of 4 to 8% at a temperature not exceeding 400 F. The dried product is then granulated at least to a size where 97% passes a U.S.S. No. 70 screen. Granulation is preferably carried out by subjecting the dried pieces to a further chopping in which they are subdivided to still smaller lengths and then granulated by means of a finishing grinder such as a ham mer mill.

The product of the present process is characterized by a certain novel characteristic. It has a uniform density at various degress of granulation, the density ranging between 550 to 650 and, more typically, between 580 and 620 grams per dry quart. The product has a soluble solids content ranging between 18 and 30%, a most unique level in the case of high density core binder materials which normally lie in the range of 7 to 10% soluble solids for dry mill stock and 7 to 14% in the case of wet mill stock. The product of the present process is characterized by its uniformly excellent foundry properties as measured by test procedures of the Steel Foundry Society of America. Among the tests which are utilized to measure the properties of a core binder in a foundry operation are green compressive strength (a measure of resistance to pressure of an unbaked test mold), green strength de* formation (a measure of resistance to deformation of an unbaked green mold), toughness (which is a measure derived mathematically from green compressive strength and green strength deformation), sag, crack and overhang (the latter three characteristics being measured in jolts).

By virtue of the excellent properties of the core binder materials of the present invention, the foundryrnan is provided with a material of moderate cost in that a lesser weight of binder composition in the order of 10 to 20% may be employed in most core formulations. The core binder material of the present invention is readily commingled with sand and water and is compatible with all known foundry core formulations.

The process is characterized by its simplicity and controllability. Although the starting material is preferably corn-derived fractions having a particle size less than 10' and more preferably less than 20 mesh, which size fraction is normally the excess of a dry corn millers production, other starch sources may be employed. These are: whole corn grits which have been granulated to the aforesaid particle size, and other ground cereal flours high in starch and semipurified or purified starches from, typically, wheat, sorghum and rye, and root starches such as tapioca and potato. The prewetting operation is relatively simple and brief, usually consuming less than two minutes. The prewetted, granulated, starch-containing material can be added directly to an extrusion cooker and its dwell time therein is usually less than one minute. The material issuing from the extrusion cooker is readily handled and dried and may be subdivided to any fineness using conventional granulation apparatus while at the same time achieving a product uniformity not matched by prior starch conversion practices characteristic of the dry and wet mill processes.

The binder material produced by the herein described process can be blended with other starch-containing binder material for differing binding characteristics.

The invention will be more fully understood by refer ence to the accompanying example.

Ground brewers corn grits (i.e., coarsely ground degerminated yellow corn) having a particle size whereat passes a U.S.S. No. 20 screen and no more than 10% passes a U.S.S. No. 100 screen, was fed to a conditioning vessel in which the farinaceous, ground corn was wetted and steamed to a moisture content of 27% through the rotation of screw flights within a cylindrical chamber. This apparatus promotes uniform mixing of the farinaceous material and steam and water introduced thereto. The corn flour was elevated in approximately 5 seconds to a temperature of F. as measured by a direct reading thermometer inserted into the throat of the discharge from the treating chamber. During this step of the process the corn flour was softened due to the uptake of moisture added in the form of steam and water; in this condition the wetted corn flour will mold to the hand when it is subjected to normal hand pressure and will retain this shape but will break apart readily when subjected to a deformation force attempting to break up the shaped piece. At this point the starch component of the corn flour had not been gelatinized materially.

The wetted corn mixture was then fed to an extrusion cooker. This extrusion cooker may comprise an intake or leading chamber, and intermediate cooking chamber and a terminal outlet chamber and working auger extending through the length of these three chambers. The flights of the auger delivered the wetted corn mixture from the leading chamber to the intermediate cooking through a mechanical seal. The screw flights decreased in pitch toward the center of the intermediate cooking chamber and increased in pitch at the extremities thereof. The free space between the surface of the auger flights and the inner surface of the cooking chamber was substantially occupied by the material being advanced therein against the back pressure of material passing through the extruding head so that the corn mixture in the cooking chamber was subjected to a combination of frictional heat and mechanical treatment by the work applied thereto as well as the heat of steam fed to the jacket for the cooking chamber. The mass was then delivered to the outer chamber of the cooker where it was subjected to a high pressure and temperature buildup due to the narrowing free space between the tapering frustoconical surface of the jacket and the complementary flights rotating therewithin as well as the restriction existing in the die plate through which the 'mass was extruded in the form of ropes. Dwell time in the extrusion cooker was 23 seconds.

By reason of the pressure and temperature build-up as the wetted corn mixture passed through the extrusion cooker, part of the moisture of the extrudate was caused to flash-off as the steam extrudate issued through the die plate, thereby causing the extrudate to expand to three to four times the volume of the dieopenings, whereafter the extrudate collapsed in a period of 1 to 2 seconds to a volume 1 /2 to 2 times the volume of the die openings. temperature of about 200 F. and, if allowed to stand at room temperature, rapidly cooled in about 2 to 3 minutes to a tough, horny, glassy form. The cooled extrudate appeared to have very tiny openings at its surface, althrough at certain points along its length it had blisters or cavities. The interior of the cooled extrudate also had the same porous structure. The moisture content of the extrudate issuing from the chamber was 21%.

The hot plastic extrudate was then fed into a corn chopper, where it was cut into lengths and deposited in a dryer having air circulating at a temperature of 300 F. therethrough to bring these lengths down to a moisturecontent of 6%. covered was fed into a second chopper adapted to produce material which passes 'a screen having A openings therein and was then ground in a hammer mill to usual flour fineness (i.e., 97% by weight of the material passing a No. 70 USS. screen or finer).

The final product had a density of approximately 609 grams per dry quart. This same product, when ground to varying degrees of granulation below the aforesaid particle size, still exhibited a product density in the range of 550 to 650 grams per dry quart. When the floury product was blended with an excess of water, a portion thereof dissolved and was filtered off. The filtrate contained soluble solids at a level equivalent to 25% of the total Weight of product admixed with the water. This farinaceous material has a green compressive strength of 0.62 p.s.i. as measured by a Universal Sand Strength Machine; a green strength deformation of 0.085 inch per inch as measured by a Dietert Sand Tester; a toughness of 35.55 as calculated from green compressive strength and green strength deformation; a sag of 8 jolts; a crack of 20 jolts; and an overhang of 32 jolts. Sag, crack and overhang were also measured on the Dietert Sand Tester.

Although the binder composition which is the subject matter of this specification has been described hereinbefore with particular reference to its use as a foundry core binder, i.e., an adhesive material for binding or aggregating particles of sand to form cores perparatory to casting in a foundry, it will be understood that the binder has other uses. for agglomerating metallic ores of such low grade as would otherwise be unworkable. It can be used as a binder for charcoal briquettes and as an emulsifying agent.

While the present invention has been described with particular reference to a specific example, it is not to be The extrudate was thermoplastic, had a The dried product re-' For example, it is also useful 6 limited thereby, but reference is to be had to the ap pended claims for a definition of its scope.

What is claimed is:

l. Binder having as a major constituent thereof a high starch farinaceous solid material of a density of from about 550 to 650 gms. per dry qt., said material having a water-soluble solids content of from about 18 to the starch content of said material being substantially gelatinized to a point where it has lost its birefringence, all of said water-soluble solids being uniformly and homogeneously distributed throughout said high-starch material in adherence with the remainder of said material.

2. Binder as claimed in claim 1, in which said farinaceous material is corn.

3. Binder as claimed in claim 2, in which said farinaceous material is selected from the group consisting of purified and semipurified starch.

4. Binder as claimed in claim 1, in which said farinaceous material is an edible tuber.

5. Binder having as a major constituent thereof a highstarch farinaceous solid material of a density of from about 580 to 620 gms. per dry qt., said material having a water-soluble solids content of from about 22 to 28%, the starch content of said material being substantially gelatinized to a point where it has lost its birefringence,

' all of said water-soluble solids being uniformly and homogeneously distributed throughout said high-starch material in adherence with the remainder of said material.

6. Binder having as a major constituent thereof a highstarch farinaceous solid material of a density of from about 550 to 650 gms. per dry qt, said material having a watersoluble solids content 'of from about 18 to 30%, the starch content of said material being substantially gelatinized to a point where it has lost its birefringence, all of said water-soluble solids being uniformly and homogene ously distributed throughout said high-starch material in adherence with the remainder of said material, said material having a moisture content of 4 to 8% and a particle size whereat at least 97% passes a U.S.S. No. 70 Screen.

7. A process for making an improved binder composition characterized by its high uniform density, which comprises prewetting a subdivided high-starch farinaceous material to a moisture content of about 20 to 30%, working the prewetted material in a closed chamber at an elevated temperature and superatmospheric pressure until a minor fraction of the original moisture content of the worked material will flash off as water vapor w en released to atmospheric pressure, said working being carried out under conditions sufficient to gelatinize at least of the starch content of the material and to partially degrade the starch so that 18 to 30% 0f the worked material is water-soluble, and releasing the worked material to the ambient atmosphere.

8. A process for making an improved binder composition characterized by its high uniform density, which comprises prewetting a subdivided, high-starch farinaceous material to a moisture content of about 20 to 30% while heating the material to a temperature of about F. to 210 F., working the prewetted material in a closed chamber at an elevated temperature and superatmospheric pressure until a minor fraction of the original moisture content of the worked material will flash oil as water vapor when released to atmospheric pressure, said work ing being carried out under conditions sufiicient to gelatinize at least 90% of the starch content of the material and to partially degrade the starch so that 18 to 30% of the worked material is water-soluble, and releasing the worked material to the ambient atmosphere.

9. A process for making an improved binder composi tion characterized by its high uniform density, which comprises prewetting a subdivided high-starch farinaceous material to a moisture content of about 20 to 30%, working the prewetted material in a closed chamber at an elevated temperature and superatmospheric pressure until about 20 to 30% of the original moisture content of the Worked material will flash off as water vapor when released to atmospheric pressure, said working being carried out under conditions sufficient to gelatinize at least 90% of the starch content of the material and to partially degrade the starch so that 18 to 30% of the Worked material is water-soluble, and extruding the Worked material to the ambient atmosphere.

10. A process for making an improved binder composition characterized by its high uniform density, which comprises prewetting a subdivided high-starch farinaceous material to a moisture content of about 23 to 28%, working the prewette d material in a closed chamber at an elevated temperature and superatrnospheric pressure until about 20 to 30% of the original moisture content of the Worked material will flash ofi as water vapor when released to atmospheric pressure, said working being carried out under conditions sufiicient to gelatinize at least 90% of the starch content of the material and to partially degrade the starch so that 22 to 28% of the worked material is water-soluble, and extruding the Worked material to the ambient atmosphere.

11. A process for making an improved binder composition characterized by its high uniform density, which comprises prewetting a subdivided, high-starch farinaceous material to a moisture content of about 20 to 30%, Working the prewetted material in a closed chamber at an elevated temperature and superatmosphenic pressure until on subsequent extrusion to the ambient atmosphere the Worked material will expand to a volume of about 300 to 400% of its uneX-panded volume and then contract to a volume of about 150 to 200% of its unexpanded volume and the starch content of the material will be partially degraded so that 18 to 30% of the worked material is water soluble, and extruding the worked material to the ambient atmosphere.

12. A process for making an improved binder composition characterized by its high uniform density, which comprises prewetting a subdivided, high-starch farinaceous material to a moisture content of about 20 to working the prewetted material in a closed chamber at an elevated temperature and superatmospheric pressure until a minor fraction of the original moisture content of the worked material will flash off as water vapor when released to atmospheric pressure, said working being carried out under conditions sufiicient to gelatinize at least of the starch content of the material and to partially degrade the starch so that 18 to 30% of the worked material is Water soluble, extruding the worked material to the ambient atmosphere, subdividing the extrudate and drying same to a moisture content of about 4 to 8%.

13. A process for making an improved binder composition characterized by its high uniform density, which comprises prewetting lower granulation fractions of degerminated, dehulled corn to a moisture content of about 20 to 30%, Working the prewetted corn in a closed chamber at an elevated temperature and superatmospheric pressure until a minor fraction of the original moisture content o-f the worked corn will flash off as water vapor when released to atmospheric pressure, said working being carried out under conditions sufiicient to golatinize at least 90% of the starch content of the corn and to partially degrade the starch so that 18 to 30% of the Worked corn is Water-soluble, and releasing said worked corn to the ambient atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS 1,979,257 Giesecke Nov. 6, 1934 2,548,263 Hofman Apr. 10, 1951 FOREIGN PATENTS 709,558 Great Britain May 26, 1954 

1. BINDER HAVING AS A MAJOR CONSTITUENT THEREOF A HIGHSTARCH FARINACEOUS SOLID MATERIAL OF A DENSITY OF FROM ABOUT 550 TO 650 GMS. PER DRY QT., SAID MATERIAL HAVING A WATER-SOLUBLE SOLIDS CONTENT OF FROM ABOUT 18 TO 30%, THE STARCH CONTENT OF SAID MATERIAL BEING SUBSTANTIALLY GELATINIZED TO A POINT WHERE IT HAS LOST ITS BIREFRINGENCE, ALL OF SAID WATER-SOLUBLE SOLIDS BEING UNIFORMLY AND HOMOGENEOUSLY DISTRIBUTED THROUGHOUT SAID HIGH-STARCH MATERIAL IN ADHERENCE WITH THE REMAINDER OF SAID MATERIAL. 